Hybrid vehicles have recently been attracting much attention as environmentally friendly vehicles. The hybrid vehicles are vehicles that run employing, as power supplies, a power storage device (battery), an inverter and an electric motor (motor) driven by the inverter, in addition to a conventional engine.
Even though the engine is started at regular time intervals, such vehicles may hardly consume fuel in a fuel tank over a long period of time because of the short driving time. In this case, fuel degradation or alteration may result in deteriorated starting capability of engine and deteriorated emission characteristics.
Japanese Patent Laying-Open No. 2005-226462 discloses a fuel supply apparatus in which a fuel pump and path switching means are provided integrally. This fuel supply apparatus is configured to be switchable between an operating state of supplying fuel in the fuel tank to a carburetor and a circulating state of returning fuel in the carburetor back to the fuel tank. When the engine is to be stopped over a long period of time, the fuel supply apparatus is controlled to be in the circulating state. This can solve inconveniences such as starting failure due to fuel degradation or alteration next time the engine is started.
When the stop period of the engine mounted on a hybrid vehicle is long, rust may be formed in pipes, for example, due to moisture separated from the fuel remaining in the pipes. Further, progress in degradation of fuel remaining in the pipes may affect the engine operation.
Conceivable as a method for preventing such problems is the method disclosed in Japanese Patent Laying-Open No. 2005-226462, i.e., the method for returning all fuel in the pipes to the fuel tank. According to this method, however, fuel is not remaining in the pipes when the traveling mode of the hybrid vehicle is set at a mode in which the engine is allowed to operate, which creates difficulty in supplying fuel to the engine immediately after starting the fuel pump. Accordingly, the engine cannot be started immediately, which may affect traveling of the hybrid vehicle.